In wellbore drilling situations that use a drilling rig, a drilling fluid circulation system circulates (or pumps) drilling fluid (for example, drilling mud) with one or more mud pumps. The drilling fluid circulation system moves drilling mud down into the wellbore through a drill string that is made up of special pipe (referred to as drill pipe) and drill collars and or other downhole drilling tools. The fluid exits through ports (jets) in the drill bit, picking up cuttings and carrying the cuttings up the annulus of the wellbore. At the surface, the mud and cuttings leave the wellbore through an outlet, and are sent to a cuttings removal system, for example, via a mud return line. At the end of the return lines, the mud and the cuttings are flowed onto a vibrating screen known as a shale shaker. Finer solids may be removed by a sand trap such as a dedicated solid removal equipment. The mud may be treated with chemicals stored in a chemical tank and then provided into the mud tank, where the process is repeated.
The drilling fluid circulation system delivers large volumes of mud flow under pressure during drilling rig operations. The circulation system delivers the mud to the drill string to flow down the string of drill pipe and out through the drill bit appended to the lower end of the drill string. In addition to cooling the drill bit, the mud hydraulically washes away the face of the wellbore through a set of jets in the drill bit. The mud additionally washes away debris, rock chips, and cuttings, which are generated as the drill bit advances. The circulation system flows the mud in an annular space on the outside of the drill string and on the interior of the open hole formed by the drilling process. In this manner, the circulation system flows the mud through the drill bit and out of the wellbore.
Sometimes a severe lost circulation zone (also known as a high-loss zone) is encountered during the drilling operation. A severe lost circulation zone is a highly permeable or fractured section in the formation where the pressure of the formation is significantly lower than the hydrostatic pressure of the drilling mud. The permeability (ease of flow through the rock formation) allows the drilling mud to enter the formation rather than return to the surface through the annulus of the wellbore. When drilling in a lost circulation zone, a large portion of or all of the drilling fluid that exits the drilling bit can be lost into the lost circulation zone instead of flowing to the surface. Such loss in drilling fluid, in a lost circulation zone can result, among other issues, in expensive downtime and loss of well control.